Seven-time title winner Valentino Rossi aims to stay in the sport for another two years

Motorcycling star Casey Stoner may have announced his attention to retire from the sport on Thursday, but his apparent lack of motivation to continue racing was not apparent 24 hours later as he topped practice for this weekend's Le Mans Grand Prix.

The two-time MotoGP world champion says he has grown tired of the discipline after five years competing in the elite division, and will bow out at the end of this season -- which still has 15 of the 18 races remaining

"I will be finishing my career at the end of this season in MotoGP, and go forward in different things in my life," the 26-year-old Australian told a pre-practice news conference.

"After so many years of doing this sport which I love, and which myself and my family made so many sacrifices for, after so many years of trying to get to where we have gotten to at this point, this sport has changed a lot and it has changed to the point where I am not enjoying it.

Bike stars gear up for MotoGP 2012 12 photos

Bike stars gear up for MotoGP 201212 photos

Stoner on track for 2012 glory – Honda's world champion Casey Stoner won 10 of the 17 completed races in MotoGP last season, including the finale in Valencia. He is hoping to retain his Qatar race title in Sunday's season opener.

Hide Caption

1 of 12

Bike stars gear up for MotoGP 201212 photos

High-flying Lorenzo – Yamaha's Jorge Lorenzo finished second at Japanese Grand Prix in October -- and second overall as the Spaniard relinquished his world title to Stoner. A finger injury ruled him out of the last three races.

Hide Caption

2 of 12

Bike stars gear up for MotoGP 201212 photos

Italy's roaring sucess on home turf – Honda's Andrea Dovizioso will be seeking his first race victory since his maiden win in 2009. The Italian placed third overall last year after registering seven podium placings.

Hide Caption

3 of 12

Bike stars gear up for MotoGP 201212 photos

Pedrosa showered in glory – Another Honda rider, Dani Pedrosa, was fourth in 2011 after missing three races due to a fractured collarbone at the French Grand Prix in May. The Spaniard was runner-up to Lorenzo in 2010.

Hide Caption

4 of 12

Bike stars gear up for MotoGP 201212 photos

Can Rossi return to form? – Seven-time world champion Valentino Rossi will seek to improve on a disappointing first season at Ducati, having ended 2011 in seventh place.

Hide Caption

5 of 12

Bike stars gear up for MotoGP 201212 photos

Success for Spies – American rider Ben Spies was Rossi's replacement at Yamaha's main team last year, and the 27-year-old won a race for the first time in the Netherlands and finished fifth overall.

Hide Caption

6 of 12

Bike stars gear up for MotoGP 201212 photos

Sparks fly for Hayden – Rossi's teammate Nicky Hayden was a world champion with Honda in 2006, but finished eighth last year and crashed in the final race. The 30-year-old American is starting his fourth season at the Italian team.

Hide Caption

7 of 12

Bike stars gear up for MotoGP 201212 photos

Crutchlow flies the flag – Britain's Cal Crutchlow was a big success in the World Superbike series, but struggled after taking the step up to MotoGP last year with the Monster Yamaha Tech 3 team.

Hide Caption

8 of 12

Bike stars gear up for MotoGP 201212 photos

Larger than life Hiroshi – Hiroshi Aoyama was the top Japanese rider in MotoGP last year. The 30-year-old finished the season 10th for the San Carlo Honda Gresini team.

Hide Caption

9 of 12

Bike stars gear up for MotoGP 201212 photos

Hector puts his head down – Spanish rider Hector Barbera has switched to the Pramac Racing team for 2012 after two years at Ducati, where he finished 12th and then 11th overall.

Hide Caption

10 of 12

Bike stars gear up for MotoGP 201212 photos

Czech cuts a fine figure – Young Czech rider Karel Abraham will be embarking on his second season in MotoGP. The 22-year-old was 14th overall for Ducati last year.

Hide Caption

11 of 12

Bike stars gear up for MotoGP 201212 photos

Remembering Marco – The starting grid will be less colorful this year due to the absence of charismatic Italian rider Marco Simoncelli, who died after crashing at the Malaysian Grand Prix in October.

Hide Caption

12 of 12

EXPAND GALLERY

"There are a lot of things that have disappointed me, and also a lot of things I have loved about this sport, but unfortunately the balance has gone in the wrong direction."

The Honda rider leads the 2012 world championship after two wins from three races.

"It would be nice if I could say I would stay one more year," he said. "But then where does it stop? So we decided to finish everything as we are now."

Stoner set a time of one minute 33.74 seconds around the French circuit on Friday, over two-tenths of a second quicker than Spanish teammate Dani Pedrosa.

Pedrosa's compatriot and 2010 world champion Jorge Lorenzo, who is one point behind Stoner in the standings, was almost four-tenths of a second adrift in third position for Yamaha.

Seven-time world champion Valentino Rossi was well down the order in ninth, having struggled for form since switching from Yamaha to Ducati for the 2011 season.

But despite his recent poor form, the legendary Italian dismissed rumors he was considering retirement and said he wanted to continue in the sport for at least another two seasons.

"For me it's very difficult to understand where the news starts because I never speak about my retirement," the 33-year-old said. "I want to race in MotoGP for the next two years for sure."